The invention relates to a device for manual fine metering of a substance, particularly in powder form, from a manual transport tool. The invention also relates to a scale with a corresponding device.
In laboratories of the chemical and pharmaceutical industries and for research purposes, very small samples of substances are used for the analysis of such substances. Sample quantities in the range of 1 mg to 50 mg are very common. The samples are often manufactured only once, so that automatic metering heads are not suitable. For manual fine metering, use is made of a high-resolution scale, onto the receiving container (for example, scale pan) of which the substance is poured utilizing a transport tool until the desired mass has been placed on the receiving container. The transport tool is typically a spatula which can easily be tipped, tapped or shaken over the receiving container of the scale so that small quantities of the substance fall from the spatula. Using this metering method which is commonplace in laboratories, it is often the case that metering accuracies of only 10% are achieved.
A device for automatic, that is, not for manual, metering is disclosed by EP 2 072 974 A1. Herein, powder is automatically poured out of a container into a vibrating funnel, from where the powder enters a container which has a small filling opening.
Vibrating spatulas are also known, in which a vibrating element is accommodated in the handle of the spatula, causing the spatula tip to vibrate and thus assisting with metering. The resulting large handle proves to be unwieldy for handling samples in the mg range.